Electric motor hammer

ABSTRACT

An electric motor hammer which comprises a support having motors and winch means mounted thereon in balanced positions and a guide rod passing through vertically aligned holes in said mounting member and having an upper portion to which one end of a length of wire rope to be wound onto said winch means is anchored and the lower end to be connected to the head of an object to be driven by said motor hammer and in which the weight of said motors itself is the gravity source and by the utilization of the motors&#39;&#39; own weight and driving force, the motor hammer is lifted by a predetermined distance until the motor hammer reaches a predetermined height whereupon the motor hammer drops by its own weight to drive the object with high impact force by the own weight and acceleration as the motor hammer drops and repeating the lifting and dropping movements until the object is driven to a predetermined position. The motor hammer is so designed that as the motors are driven in one direction, the entire support is lifted up along the guide rod through the winch means until the support reaches the predetermined position whereupon the motors are stopped and the entire support is released whereby the support is allowed to drop together with the motors and winch means so as to drive the object with a high impact generated by the weight of the entire support and acceleration as the support drops.

United States Patent [1 1 Watanabe 1 Oct. 22, 1974 1 ELECTRIC MOTOR HAMMER [76] Inventor: Hikoitsu Watanabe, No. 5-13,

l-chome, Ebara-cho, Tokyo, Japan [22] Filed: Dec. 10, 1973 [21] Appl. No.: 423,098

[52] US. Cl 173/53, 173/81, 173/126 [51] Int. Cl E211) U00, E02d 7/00 [58] Field of Search 173/81, 83, 84, 126, 132,

[56] References Cited UNITED STATES PATENTS 2,378,131 6/1945 Dirksen et a1. 173/53 2,487,530 11/1949 Dirksen l l 4 173/53 2,659,584 11/1953 Dorkins 173/124 3,009,522 11/1961 Bedner 173/125 3,157,235 11/1964 Raizk et a] 173/53 3,612,188 10/1971 Takenosuke Ono.... 173/122 3,713,498 l/l973 Watanabe et a1 173/53 Primary Examiner-James A. Leppink Attorney, Agent, or FirmSaul Jecies having motors and winch means mounted thereon in balanced positions and a guide rod passing through vertically aligned holes in said mounting member and having an upper portion to which one end of a length of wire rope to be wound onto said winch means is anchored and the lower end to be connected to the head of an object to be driven by said motor hammer and in which the weight of said motors itself is the gravity source and by the utilization of the motors own weight and driving force, the motor hammer is lifted by a predetermined distance until the motor hammer reaches a predetermined height whereupon the motor hammer drops by its own weight to drive the object with high impact force by the own weight and acceleration as the motor hammer drops and repeating the lifting and dropping movements until the object is driven to a predetermined position. The motor hammer is so designed that as the motors are driven in one direction, the entire support is lifted up along the guide rod through the winch means until the support reaches the predetermined position whereupon the motors are stopped and the entire support is released whereby the support is allowed to drop together with the motors and winch means so as to drive the object with a high impact generated by the weight of the entire support and acceleration as the support drops.

7 Claims, 8 Drawing Figures PATENIED 3,842,916

SIEET EMF 5 ELECTRIC MOTOR HAMMER BACKGROUND OF THE INVENTION This invention relates to an electric motor hammer and more particularly, to an electric motor hammer for use in driving a pile at a construction site, for example.

In most of existing pile driving machines, a weight hammer slidably received on an upright guide rod having a suitable length is lifted up along the guide rod by means of a winch to a predetermined position along the guide rod and the hammer is then allowed to drop by its own weight by releasing the winch, or a rod-like hammer is lifted by use of explosive power produced within a cylinder and is then dropped.

However, in such prior art devices a hammer is incapable of moving up by itself and therefore, the hammer must be lifted by means of separate means such as a winch or explosive power produced in a cylinder. Thus, the weight hammer has only a sole function as driving hammer and requires separate means for actuating the hammer. Thus, the conventional devices are inevitably large in size and complicate in manipulation.

SUMMARY OF THE INVENTION Therefore, one object of the present invention is to provide an electric motor hammer in which a weight hammer is capable of rising up by itself without help of any separate lifting means and capable of rising up limitlessly along a guide rod the length of which can be increased by connecting an additional rod or rods thereto as well as increasement of the length of a wire rope to thereby provide a long dropping stroke of the hammer resulting in high impact force.

Another object of the present invention is to provide an electric motor hammer in which a motor support supports winchtype hoist means thereon and the support moves upwardly and downwardly along a guide rod as a winch mechanism is operated by motor means.

Another object of the present invention is to provide an electric motor hammer in which a motor support is lifted and allowed to drop to deliver a high impact force to an object to be driven by operating a winch mechanism through pawled clutch plates which are engaged to each other by the energization of a solenoid for lifting the motor support and are disengaged from each other by the energization of the solenoid to thereby stop so as to allow the support to drop by its own weight.

Another object of the present invention is to provide an electric motor hammer in which an electromagnetic clutch is provided in the winch mechanism for lifting or allowing the motor support to drop by its own weight so as to impart impact to an object to be driven.

An optional object of the present invention is to provide an electric motor hammer which is simple in construction and manipulation and can be produced at less expense for attaining the above objects.

The present invention is characterized in that the motor support is capable of moving up by itself without help of any separate lifting means, the lifting distance of the hammer can be increased limitlessly by adding an additional rod or rods to the guide rod so as to produce an increased dropping stroke distance for the hammer, the driving operation by the hammer is improved by repeating upward and downward movements of the hammer in the increased dropping stroke distance accompanied by a high impact force and the hammer is simple in construction and manipulation resulting in great saving in operation time.

The above and other objects and attendant advantages of the present invention will be more readily apparent to those skilled in the-art from a reading of the following detailed description in conjunction with the accompanying drawings which show preferred embodiments of the invention for illustration purpose only. but not for limiting the scope of the same in any way.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a front elevational view of a first embodiment of electric motor hammer constructed in accordance with the present invention.

FIG. 2 is a top plan view of FIG. 1.

FIG. 3 is similar to FIG. 1, but shows the electric motor hammer together with a pile being driven by the hammer.

FIG. 4 is a front elevational view of a second embodiment of electric motor hammer constructed in accordance with the present invention.

FIG. 5 is a top plan view of FIG. 4.

FIG. 6 is a fragmentary top plan view on an enlarged scale of portion of FIG. 5.

FIG. 7 is a fragmentary front elevation view of a modified form of winch mechanism with portion thereof broken away.

FIG. 8 is similar to FIG. 4, but shows the electric motor hammer together with a pile being by the hammer.

DESCRIPTION OF PREFERRED EMBODIMENTS The present invention will be now described referring to the accompanying drawings and more particularly, to FIGS. 1 through 3 inclusive in which a first embodiment of electric motor hammer of the invention is shown.

The electric motor hammer generally comprises a pair of juxtaposed motors 11, II fixedly mounted within a common support 12 in spaced parallel relationship and the support has an impact receiving 13 secured to the undersurface thereof for reinforcing and protecting the support against impact which may be otherwise directly received by the support when the hammer strikes against a pile to drive the same into the ground, for example. The support I2 is in the form of a housing having an elliptic shape in cross-section as seen in horizon and the top and bottom walls of the support are provided with vertically aligned through holes I5 and 16, respectively which normally lie in the plane of the axis of the support when the impact assembly in its balanced position. The impact receiving plate 13 is also provided with a thorough hole in alignment with the holes 15, 16in the support 12. The holes in the support 12 and impact receiving plate 13 are adapted to slidably receive a guide rod 14 along which an impact assembly of which description will be made hereinafter can slidably move upwardly and downwardly in a manner as will be described hereinafter. Each of the motors II, II is fixedly mounted on its associated transverse rotary shaft 17 for rotational movement therewith and has a smaller pulley I8 fixedly secured to one end. As seen from FIGS. 1 and 3, the smaller pulley 18 associated with the shaft I7 for one of the pair of motors 11, 11 is positioned on one side the support 12 and smaller pulley 18 associated with the shaft 17 for the other motor is positioned on the other or opposite side of the support.

A pair of spaced winch drum shaft support brackets 19, 19 are secured to and extending uprightly from the top wall of the support 12 in opposition to each other and at an equal distance from the hole 16. A winch drum shaft 20 is journalled at the opposite ends in the support brackets l9, 19 for rotational movement therein and a winch drum 22 is fixedly mounted on the shaft 20 for rotational movement therewith. A length of wire rope 21 is wound about the drum 22 with one end anchored thereto to be payed out of and retracted onto the drum.

The drum shaft 20 extends at the opposite ends through the opposite support brackets l9, l9 and has larger pulleys 23, 23 secured to the opposite end extensions. An endless belt 24 is trained over each associated smaller and larger pulley unit 18 and 23 to drivingly connect the pulleys in interlocking relationship.

When the above-mentioned drive mechanism is mounted on the support 12 in the mentioned hereinabove, it will be anticipated that the entire support will be out of balance to thereby displace the holes and 16 in the support from the plane of the normal axis of the support 12 which in turn impede slidable movement of the entire support along the guide rod 14. Thus, in order to compensate for such displacement of the holes, according to the present invention, a counterweight 25 is fixedly mounted on the uppersurface of the top wall of the support l2 on the side of the hole 16 opposite from the winch drum 22.

An electric cord 26 is electrically connected to and extends from each of the motors 11, I1 and there is the possibility that the cords will break or cut and/or swing violently on an account of violent vibration or tremor which the cords is delivered to them by high impact which generates when the motor hammer is operated for pile driving. For the protection of the cords 26 against such breaking and/or violent swing, according to the present invention, each cord 26 is passed through a through hole (not shown) in the associated support bracket 19 and then extended out of the support bracket. The cord extensions are put together and covered by a cabtyre 27. The cabtyre-covered cord assembly is guided to a switchable switch box (not shown) or the like which incorporates a timer (not shown) therein.

In the embodiment shown in FIGS. 1 through 3 inclusive as described hereinabove, the reason for which the pulleys I8 and 23 are formed with different diameters is that when the winch drum 22 is rotated at a normal rotation rate ofthe motors II, II, there is the possibility that the motor hammer will be lifted at an excessively accelerated high rate. In addition, the difference in diameters between the pulleys I8 and 23 serves as reduction means for increasing the output of the motors. However, these features do not constitute any essential part of the present invention, but may be eliminated if the electric motor hammer is desired to be lifted at a high rate and the motors are not required to increase their output.

Furthermore. according to the present invention, the illustrated pulley-belt arrangement as the interlocking means between the motors ll, 11 and drum 22 may be replaced by any other suitable interlocking means such as a sprocket-chain arrangement within the scope of the invention. In the embodiment as shown in FIGS. 1 through 3 inclusive and described hereinabove, the position of the winch drum 22 on the support 12 should be so selected that the drum is positioned in a position close as much as possible to the guide rod 14 passing through the holes in the mounting member 12 and impact receiving plate 13, but out of the wire ropes way as the rope is payed out of and wound onto the winch drum 22 as the drum is rotated in one or the other direction as shown in FIG. 3.

In the embodiment as shown in FIGS. I through 3 inclusive and described hereinabove, although the two juxtaposed motors 11, 11 are provided, the two motors may be replaced by only one motor within the scope of the invention. When only one motor is employed, the motor and the afore-mentioned counterweight 25 are fixedly mounted on the top wall of the support 12 in a suitably spaced relationship to each other so as to maintain the entire support in balanced position. Except for the guide rod 12 and switch box, the aforementioned components of the electric motor hammer constitute an impact assembly.

Now, the operation of the embodiment of FIGS. 1 through 3 inclusive will be described referring to FIG. 3 more particularly.

In FIG. 3, a pile to be driven into the ground G is shown with reference numeral 29. Prior to the initiation of a cycle of pile driving operation, a striking cap 31 having a center hole 30 is put on the upper end portion of the pile 29. The lower end portion of the guide rod 14 is then passed through the aligned holes 15 and 16 in the top and bottom walls of the support 12 and also the hole in the impact receiving plate 13 into the center hole 30 in the striking cap 31 and set therein and thereafter, the free end of the wire rope 21 is payed out of the drum 22 upwardly along the guide rod I4 to a predetermined or desired point adjacent the upper end of the latter and anchored to the rod by means of a suitable rope clamp means 32 mounted on the guide rod to thereby complete the preliminary operation for driving the pile 29 into the ground G.

In operation, the switch box (not shown) electrically connected to the cabtyre coard assembly 26 is energized to rotate the motors 11, 11 in the wire rope winding up direction. The rotation of the motors 11, II in such a direction also rotates the winch drum 22 in the rope winding up direction to wind the rope 21 onto the drum 22. As the wire rope 21 is wound onto the winch drum 22, the entire support is lifted along the guide rod 14 to a predetermined or desired height on the rod whereupon the timer incorporated in the switch box is actuated to deenergize the switch in the switch box. Simultaneously, the motors 11, ll cease to rotate. Thereupon the impact assembly is allowed to drop along the guide rod 14 at an accelerated rate by its own gravity to strike against the pile 29 at the striking cap 30 thereon so as to drive the pile into the ground.

After the driving stroke, the impact assembly is automatically lifted along the guide rod 14 by energizing the switch is again energized to rotate the motors 11, II in the rope winding up direction which in turn rotates the drum 22 in the rope winding up direction until the impact assembly reaches the predetermined highest position ready for the next pile driving operation. The energization and deenergization of the switch is effected automatically under the control of the timer.

Referring now to FIGS. 4 through 6 inclusive and FIG. 8 in which a second embodiment of electric motor hammer of the invention is shown.

The second embodiment of electric motor hammer generally comprises an impact assembly including a support 12a in the form of a horizontally extending rectangular housing and a pair of juxtaposed motors 11a, 11a mounted within the housin in spaced relationship. The bottom and top walls of the support 120 are provided in the center thereof with aligned through holes 150 and 16a, respectively which are normally positioned in the plane of the axis of the support and through which a guide rod 140 extends. A pair of rollers 32, 32 are provided within the support 12 on the opposite sides of each of the holes 150, 16a in rolling contact with the opposite sides of the guide rod 14a so that the impact assembly can smoothly move downwardly and upwardly along the guide rod 140. For the purpose, each pair of rollers 32, 32 slightly overlie the associated hole 15a or 16a. The impact assembly of the second embodiment further includes a modified wire rope operation mechanism which is improved over the winch drum of the first embodiment.

The space between the motors 11a, 11a is preferably so selected that they may be out of the guide rod l4as way.

A wire rope winding mechanism is provided on the uppersurface of the top wall of the support 120 and includes a winch drum 22a positioned in a position close to the hole 160 in the top wall of the support 12a to the extent that the rope winding mechanism will not be in the guide rods way as the rod enters the hole 160. The drum 220 has a spiral groove 0 in the peripheral surface and a length of wire rope 21a is wound on the drum along the groove a with one end anchored to the drum. A clutch plate 33 having an outwardly directing pawl 33a is fixedly mounted on one or inner end face of the drum 22a and a drum shaft 200 extends along the longitudinal axis of the drum for rotating the drum therewith. The opposite ends of the drum shaft a extend beyond the adjacent ends of the drum and are journalled in a pair of shaft support brackets 19a, 19a which are in turn fixedly mounted on and extend uprightly from the uppersurface of the top wall of the support 120 adjacent the opposite ends of the drum shaft. The drum shaft 200 is formed with key means 34 at one end opposite to the end face of the drum 22a where the clutch plate 33 is provided and a cooperating clutch plate 35 having an inwardly directing pawl 35a is also provided at the afore-mentioned one or inner end of the drum shaft 20a for slidable movement along the key means 34 so as to engage and disengage from the clutch plate 33, having the pawl 330.

A return spring 36 is provided on the shaft 20a between the clutch plate 35 and the adjacent shaft support bracket 19a for normally urging the pawl 35a on the clutch 35 against the pawl 33a on the cooperating clutch plate 33 so that the two clutch plates will interlock. A ring 60 is disposed on the shaft 20a between the end of the drum 22a opposite from the clutch 35 and the other support bracket 19a for limiting lateral movement of the drum 220 along the shaft 200.

The periphery of the clutch plate 35 is formed with an annular groove 37 in which the free ends of pins 40, 40 at the free ends of a pair of upper and lower clutch arms 38, 38 which embrace the clutch plate 35 from above and below, respectively, engage. The clutch arms 38, 38 are pivoted at a fixed point or in the center, for example, to the top wall of the support 12a by means of a common pin 39 or the like so as to provide the fulcrum P about which the arms pivot. The other ends of the clutch arms 38, 38 are pivotally connected through a pin 41 to a solenoid 42 which is in turn suitably mounted on the top wall of the support l2a.

The clutch mechanism to be employed in the present invention is not necessarily limited to the arrangement as illustrated and described hereinbefore. For example, it will occur to those skilled in the art that if the clutch plates 33 and 35 are arranged to engage at an angle of 45 and the electro-magnetic force of the solenoid 42 is increased, the deenergization of the solenoid 42 will allow the clutches 33 and 35 to automatically disengage from each other without the provision of the aforementioned return spring 36.

The interlocking mechanism for the second embodiment of electric motor hammer is substantially identical with that described in connection with the first embodiment hereinbefore. That is, each of the shafts 17a, 17a of the two motors 11a, 11a has a smaller diameter pulley 18a secured to one end of the shaft for rotation therewith, the opposite ends of the winch drum shaft 200 which extend beyond outwardly of the respective shaft support brackets 19a, 19a have larger diameter pulleys 23a 23a secured to the opposite ends and endless belts 24a, 24a are trained over the respectively associated smaller and larger pulley units 18a, 23a, respectively. The arrangement of the smaller diameter pulleys 180 on the shafts 170 are the same as those of the first embodiment. As described in connection with the first embodiment, the pulley and belt arrangement as drive connection means may be replaced by an other suitable arrangement such as a chain and sprocket arrangement within the scope of the invention. And the provision of the pulleys having different diameters is simply for providing reduction means. The reduction ratio between these different diameter pulleys can be, of course, varied as desired or necessary.

Although the second embodiment of electric motor hammer is shown and described as having two motors 11a, lla, only one of such motors may be employed without departing from the spirit of the invention. In such case, the opposite ends of the shaft of the singly motor are operatively connected to the opposite ends of the shaft of the drum by means of a pulley-belt or sprocket-chain arrangement, respectively.

in FIGS. 5 and 6, reference numeral 43 denotes a guide rod for a length of a wire rope 21a and the guide is positioned adjacent the periphery of the drum 22a with the axis of which extending in parallel to that of the drum so that the wire rope can be wound uniformly on the drum. Reference numeral 250 denotes a counterweight positioned on top wall of the mounting member 12:: on the side of the opening 16a in the support top wall opposite from the drum 22a in order to compensate for any deviation of the holes and from the plane of the axis of the impact assembly which may occur as the result of the mounting of the winch mechanism on the support 120 to thereby maintain the assem bly in balanced position. Reference numeral 26a denotes an electric cord electrically connected to each of the motors U0, U0 and assembled together. The cord assembly 26a is then combined to a similar electric cord extending from the solenoid 42. The resultant cord assembly is covered and protected by a cabtyre 27a or the like and leads to a switch box or the like (not shown). As described in connection with the first embodiment, the switch box of the second embodiment also has a switch and a timer incorporated therein for control the peration of the impact assembly.

The operation of the second embodiment motor of hammer will be described referring to FIG. 8. Prior to the operation, the upper end of a pile 29a to be driven into the ground G is first received in the pile receiving recess of a striking cap 310 and the lower end of the guide rod 140 is set in the set hole 300 in the cap The free end of the wire rope 21a is then payed out of the drum 220 by a predetermined or desired length along the guide rod 14a and clamped to a position adjacent the upper end of the guide rod 14a by means of a clamp means 320. Thereafter, the switch in the switch box (not shown) electrically connected to the cabtyre cord assembly is energized to rotate the motors 11a, 11a in the wire rope winding up direction. The rotation of the motors 11a, 11a in such a direction also rotates the winch drum 22a in the rope widing up direction to wind the wire rope 21a onto the drum 22a until the impact assembly is lifted to a predetermined height along the guide rod 140 whereupon the motors are stopped and simultaneously, the solenoid 42 is energized to pivot the arms 41, 41 about the fulcrum P so as to disengage the clutch plate 35 from the clutch plate 33 whereby the impact assembly is allowed to drop by its own weight to strike the pile 290 at the striking cap 31a so as to drive the pile into the ground G. After the driving operation, the impact assembly is lifted by deenergizing the solenoid 42 and energizing the switch. The operation of the electric motor hammer of the second em-,

bodiment described above is, of course, automatically controlled by the timer (not shown) in the switch box.

FIG 7 shows a modified winch mechanism which employs electro-magnetic clutch means instead of the afore-mentioned clutch plates.

Referring to FIG. 7, a winch drum shaft 20b is journalled at the opposite ends in a pair of support brackets 19b, 19b and mounts a winch drum 22b having a length of wire rope 21b wound thereon for unison rotation. A flange 44 is provided at one end or the left-hand of the drum 22b (as seen in FIG. 7) and has a plurality of peripherally spaced friction members 45 mounted therein and the drum shaft 20b is formed with key means 46 adjacent one or the left-hand end thereof (as seen in FIG. 7). A pusher plate 47 is mounted at the left-hand end of the drum shaft 20b in opposition to the friction members 45 for slidable movement along the key means 46 and an annular friction plate 48 is loosely positioned between the friction members 45 and pusher plate 47 normally spaced from the friction members 45.

An electro-magnetic coil holder 49 of U-shape is secured to the inner surface of the left-hand support bracket 19a (as seen in FIG. 7) opening toward the pusher plate 47 and an electro-magnetic coil 50 is received in the holder in opposition to the pusher plate 47. Thus, when the electromagnetic coil 50 is energized, the coil urges the pusher plate 47 and accordingly, the friction plate 48 against the friction members 45 to thereby impart rotation to the drum 22b.

It is to be understood that various variations and modifications of the invention may be made without departing from the scope of the invention. It is also to be understood that the scope of the invention is not to be understood as limited to the specific embodiments disclosed herein, but only in accordance with the appended claims when read in light of the foregoing disclosure.

What is claimed is:

1. An electric motor hammer comprising a support having at least one motor and hoist means fixedly mounted thereon in balanced positions and provided with vertically aligned holes; and an upright guide rod passing through said holes and having clamp means in a position adjacent the upper end to which one end of a length of wire rope to be wound on said hoist means is anchored and a striking cap at the lower end, said striking cap being adapted to receive the upper end of an object to be driven by said motor hammer, whereby when said motor is driven, the entire support is lifted along said guide rod to a predetermined position whereupon the motor is stopped and the support is released so as to allow the entire support to drop by its own weight to deliver a high striking impact to said obect.

2. The electric motor hammer as set forth in claim 1, further comprising shaft support brackets fixedly mounted on said support, a shaft journalled in said support brackets, a winch drum of said hoist means supported on said shaft for rotation therewith, a pawled clutch plate mounted on one end face of said drum, a cooperating pawled clutch keyed to said shaft in opposition to said clutch plate on the drum for engaging with and disengaging from the latter, and a solenoid for bringing said clutch plate on the shaft into engagement with said clutch plate on the drum and disengaging the clutch plates from each other.

3. The motor hammer as set forth in claim 1, further comprising shaft support brackets fixedly mounted on said support, a shaft journalled in said support brackets, a winch drum of said hoist means rotatably supported on said shaft for rotation therewith and having at one end a flange provided with friction members a pusher plate keyed to said shaft adjacent to said friction members, a friction plate freely mounted on said shaft between said friction plate on the shaft and said friction members on the drum for engaging with and disengaging from said friction members, an electromagnetic coil holder mounted on said shaft on the side of said pusher plate opposite from said friction plate, and an electromagnetic coil adapted to be energized or deenergized so as to bring said friction plate into engagement with said friction members and disengaging the friction plate from said friction members to thereby hold said drum in position and release the drum.

4. The electric motor hammer as set forth in claim 1, further comprising rollers rotatably mounted on said support adjacent said hole means for rolling contact with said guide rod.

5. The electric motor hammer as set forth in claim 1, further comprising an electro-magnetic clutch mechanism including friction members mounted in a flange at one end of said drum, a slidable pusher plate keyed to said drum shaft in opposition to said friction members, an annular friction piece freely positioned between said friction members and pusher plate, an electro-magnetic holder fixedly mounted on one of said brackets on the side of said pusher plate opposite from said friction plate and an electromagnetic coil for moving said pusher and friction plates toward and away from said friction members.

6. An electric motor hammer comprising a normally upright guide rod having clamp means adjacent the upper end and the lower end adapted to be connected to an object to be driven by said hammer; an impact assembly mounted on said guide rod for longitudinal movement along the rod, said impact assembly comprising a support having hole means through which said guide rod passes, at least one motor rotatably mounted on said support, a winch mechanism mounted on said support and drivingly connected to said motor, said winch mechanism including a drum shaft journalled in brackets mounted on said support, a drum rotatably supported on said shaft and a length of wire rope wound on said drum with one end anchored to the drum and the other end clamped to said guide rod by said clamp means, a counterweight mounted on said support for balancing the entire support, conductor means electrically connected to said motor and timer switch means electrically connected to said motor through said conductor for driving the motor.

7. The electric motor hammer as set forth in claim 6, further comprising a clutch mechanism including a pawled clutch plate mounted on one end face of said drum, a second pawled clutch plate mounted on said drum shaft in opposition to said first clutch plate for engaging and disengaging from the latter, a pair of clutch arms engaging said second clutch plate at one end and pivoted in the center to said support, for moving said second clutch plate toward and away from said first clutch plate and a solenoid having the other ends of said clutch arms pivoted thereto and mounted on said support so as to pivot said clutch arms.

I l 1! l 

1. An electric motor hammer comprising a support having at least one motor and hoist means fixedly mounted thereon in balanced positions and provided with vertically aligned holes; and an upright guide rod passing through said holes and having clamp means in a position adjacent the upper end to which one end of a length of wire rope to be wound on said hoist means is anchored and a striking cap at the lower end, said striking cap being adapted to receive the upper end of an object to be driven by said motor hammer, whereby when said motor is driven, the entire support is lifted along said guide rod to a predetermined position whereupon the motor is stopped and the support is released so as to allow the entire support to drop by its own weight to deliver a high striking impact to said object.
 2. The electric motor hammer as set forth in claim 1, further comprising shaft support brackets fixedly mounted on said support, a shaft journalled in said support brackets, a winch drum of said hoist means supported on said shaft for rotation therewith, a pawled clutch plate mounted on one end face of said drum, a cooperating pawled clutch keyed to said shaft in opposition to said clutch plate on the drum for engaging with and disengaging from the latter, and a solenoid for bringing said clutch plate on the shaft into engagement with said clutch plate on the drum and disengaging the clutch plates from each other.
 3. The motor hammer as set forth in claim 1, further comprising shaft support brackets fixedly mounted on said support, a shaft journalled in said support brackets, a winch drum of said hoist means rotatably supported on said shaft for rotation therewith and having at one end a flange provided with friction members a pusher plate keyed to said shaft adjacent to said friction members, a friction plate freely mounted on said shaft between said friction plate on the shaft and said friction members on the drum for engaging with and disengaging from said friction members, an electromagnetic coil holder mounted on said shaft on the side of said pusher plate opposite from said friction plate, and an electromagnetic coil adapted to be energized or deenergized so as to bring said friction plate into engagement with said friction members and disengaging the friction plate from said friction members to thereby hold said drum in position and release the drum.
 4. The electric motor hammer as set forth in claim 1, further comprising rollers rotatably mounted on said support adjacent said hole means for rolling contact with said guide rod.
 5. The electric motor hammer as set forth in claim 1, further comprising an electro-magnetic clutch mechanism including friction members mounted in a flange at one end of said drum, a slidable pusher plate keyed to said drum shaft in opposition to said friction members, an annular friction piece freely positioned between said friction members and pusher plate, an electro-magnetic holder fixedly mounted on one of said brackets on the side of said pusher plate opposite from said friction plate and an electromagnetic coil for moving said pusher and friction plates toward and away from said friction members.
 6. An electric motor hammer comprising a normally upright guide rod having clamp means adjacent the upper end and the lower end adapted to be connected to an object to be driven by said hammer; an impact assembly mounted on said guide rod for longitudinal movement along the rod, said impact assembly comprising a support having hole means through which said guide rod passes, at least one motor rotatably mounted on said support, a winch mechanism mounted on said support and drivingly connected to said motor, said winch mechanism including a drum shaft journalled in brackets mounted on said support, a drum rotatably supported on said shaft and a length of wire rope wound on said drum with one end anchored to the drum and the other end clamped to said guide rod by said clamp means, a counterweight mounted on said support for balancing the entire support, conductor means electrically connected to said motor and timer switch means electrically connected to said motor through said conductor for driving the motor.
 7. The electric motor hammer as set forth in claim 6, further comprising a clutch mechanism including a pawled clutch plate mounted on one end face of said drum, a second pawled clutch plate mounted on said drum shaft in opposition to said first clutch plate for engaging and disengaging from the latter, a pair of clutch arms engaging said second clutch plate at one end and pivoted in the center to said support, for moving said second clutch plate toward and away from said first clutch plate and a solenoid having the other ends of said clutch arms pivoted thereto and mounted on said support so as to pivot said clutch arms. 